1. Field of the Invention
The present invention pertains generally to the field of cryo therapy. More particularly, the present invention pertains to cryo balloon therapy catheters for use in causing cold-induced necrosis.
2. Description of the Related Art
A number of medical conditions may be treated using ablative techniques or devices. Ablative techniques, generally, result in the necrosis of abnormal tissue at an area of interest. Ablation of the abnormal tissue may result in an efficacious treatment for a medical condition. For example, atrial fibrillation may be the result of abnormal electrical activity in the left atrium and the pulmonary vein, and may be treatable by ablation of the abnormal tissue within the left atrium and/or the pulmonary vein.
Atrial fibrillation is a serious medical condition that is the result of abnormal electrical activity within the heart. This abnormal activity may occur at regions of the heart including the sino-atrial (SA) node, the atriovenricular (AV) node, the bundle of His, or within other areas of cardiac tissue. Moreover, atrial fibrillation may be caused by abnormal activity within a isolated focal center within the heart. It is believed that these foci can originate within the pulmonary vein, particularly the superior pulmonary veins.
Minimally invasive techniques have been described that use ablation catheters to target the pulmonary vein with the hope of ablating foci having abnormal electrical activity. The techniques typically are characterized by application of energy to cause lesions within the foci or other areas possessing abnormal electrical activity.
Some ablation devices utilize radio frequency (RF) energy for ablation, including the device disclosed in U.S. Pat. No. 6,024,740 to Lesh et al. The RF energy devices may be used to ablate an area of interest with heat. The use of RF energy for ablation may, however, lead to untoward healing responses such as collagen build up at the area of interest after treatment. Moreover, RF ablation of within an atrium may decrease atrial output. A need, therefore, exists for ablative devices and methods that include improved healing responses.
An alternative treatment strategy has been developed that uses cooling energy for ablation. This method, termed cryoplasty or cryo balloon therapy, may be used to cool the lesion to freeze a portion of the affected area. For example, cryo balloon therapy may be used to freeze a lesion within a blood vessel that might otherwise lead to restenosis or recoil.
In addition to its potential utility in preventing and slowing restenosis and addressing recoil, cryo balloon therapy may be used for ablation techniques. For example, cryo balloon therapy may be efficacious in varicose vein treatment of incompetent valves, valvular disease, mitral valve regurgitation therapy, atrial fibrillation, gastric reflux disease, gastro esophageal reflux disease, GURD, esophageal disease, cancer treatment including stomach or uterine cancer, etc.
Uses of cryo balloon therapy include cold-induced necrosis of cells within the body. When the target area is located within the heart or pulmonary vasculature, it may be important to precisely control the cryo balloon therapy catheter to necrosis only the desired tissue. Precise temperature regulation may be required to necrosis target tissues while minimizing damage to healthy tissue. Moreover, precise temperature monitoring may be useful in target areas that have an uneven surface, such as trabeculae within the heart. A need, therefore, exists for cryoplasty catheters with precise temperature monitoring capabilities.